1. Field of the Invention
The invention relates to a method for removing foreign bodies from a first tobacco stream, wherein the first tobacco stream is conveyed in the region of a first foreign body detection device with an air flow, and wherein foreign bodies in the first tobacco stream are detected based on at least one property by means of the first foreign body detection device and subsequently removed from the first tobacco stream by a jet of compressed air, so that the first tobacco stream freed from foreign bodies and a second stream of tobacco particles and foreign bodies entrained by the jet of compressed air are formed.
2. Discussion of Background Information
The invention further relates to a device for removing foreign bodies from a first tobacco stream with a device (feed device) feeding the first tobacco stream to a first foreign body detection device and a first foreign body ejection device downstream of the first foreign body detection device, wherein the feed device for conveying the first tobacco stream has a compressed air source, and wherein the first foreign body ejection device has a first nozzle device, by means of which foreign bodies can be removed from the first tobacco stream with compressed air, whereby a second stream of foreign bodies and tobacco particles entrained by the compressed air is formed.
A method for removing foreign bodies from a tobacco stream and a corresponding device are known, e.g., from DE 10 2004 015 463 B4. Through this method and this device it is known how to examine a tobacco stream for foreign bodies with a high tobacco throughput and to separate foreign bodies accordingly.
The property that is used to detect the foreign body in the tobacco stream can hereby be in particular and also in the scope of the invention an optical property of the tobacco or the foreign body, such as the brightness, shape and/or color or another physical property such as the moisture, the specific weight or the presence of corresponding elements (carbon or metals).
The foreign body detection is carried out preferably by means of recording the brightness and/or color of the objects contained in the tobacco stream. In this context, objects in particular refers to tobacco, tobacco leaves, cut tobacco and foreign bodies. The conveyor speed of the tobacco stream according to DE 10 2004 015 463 B4 as well as according to the invention is between 6 m/s and 30 m/s, in particular between 17 m/s and 30 m/s. The preferred speed means that a very effective conveyance of the tobacco stream is provided, whereby a very high throughput is rendered possible. In particular, the embodiments according to DE 10 2004 015 463 B4 with respect to the drawing apart of the tobacco stream transversely to the conveying direction in the one direction and the tapering of the tobacco stream crosswise to the conveying direction and in the other direction, which is also transverse to the one direction, are also provided.
From EP 1 838 464 B1 a method and a device are known for sorting a stream of in general flat and lightweight articles of different dimensions, wherein the articles to be removed are drawn out from the main stream with suction air by means of suction action through a vacuum.
From EP 1 576 897 B1 a device and a method are known for scanning and sorting tobacco leaves, wherein a rejection device is provided which reacts to a rejection signal and is configured to force unacceptable tobacco leaves and undesirable particles from the conveyor duct.
The devices and the method according to the prior art all have the disadvantage that after the removal of the foreign bodies, the tobacco leaves that have been removed with them but are actually good or acceptable are removed in relatively large quantity, so that a relatively large loss of tobacco is incurred. This necessitates a resorting, which in the prior art is carried out on conveyor belts in an optical method. This leads to a very high expenditure in terms of equipment and nevertheless to suboptimal results.